The discussion of the background of the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any of the claims.
Ophthalmic lenses intended to be held in a frame usually involve a prescription. The ophthalmic prescription can include a positive or negative power prescription as well as an astigmatism prescription. These prescriptions correspond to corrections enabling the wearer of the lenses to correct defects of his vision. A lens is fitted in the frame in accordance with the prescription and with the position of the wearer's eyes relative to the frame.
For presbyopic wearers, the value of the power correction is different for far vision and near vision, due to the difficulties of accommodation in near vision.
The prescription thus comprises a far-vision power value and an addition, or power progression, representing the power increment between far vision and near vision; this comes down to a far-vision power prescription and a near-vision power prescription. Lenses suitable for presbyopic wearers are progressive addition lenses. Examples of progressive addition lenses are described in U.S. Pat. No. 5,270,745.
Progressive addition ophthalmic lenses include a far-vision zone, a near-vision zone and an intermediate-vision zone, a principal progression meridian crossing these three zones. They are generally determined by optimization, based on a certain number of constraints imposed on the different features of the lens.
Some wearers may have difficulties to adapt to the use of progressive addition lenses despite normal binocular vision and other normal clinical findings.
There is a need for simple and reliable tests to try to determine if a wearer is likely to accept or not the use of progressive addition lenses.
Clinical indicators that potentially predict non acceptance of progressive addition lenses may include strabismus, amblyopia, anisometropia, convergence insufficiency or retinal diseases in general.
Linking the above mentioned clinical indicators to the acceptance of progressive addition lenses appears not to be exhaustive and always very reliable.
Therefore, there is a need for a reliable and simple method for determining the acceptance of progressive addition lenses of a wearer.
One object of the invention is to provide a method for determining the acceptance of progressive addition lenses of a wearer that does not present the drawbacks mentioned hereinabove.